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Modified Natural Frozen Embryo Protocol
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The Florida Institute for Reproductive Medicine (F.I.R.M.) offers the modified natural frozen embryo transfer (FET) protocol to eligible patients at its clinics in Jacksonville, Daytona Beach, Tallahassee, and Valdosta, GA. In a modified natural FET cycle, the patient's own natural ovulation cycle is used to time the embryo transfer, with a small amount of medication added to support implantation — typically a trigger shot to control the timing of ovulation. This approach avoids the heavier hormone regimens used in medicated FET cycles and is often preferred by patients who ovulate regularly and want a more natural protocol.
The Florida Institute for Reproductive Medicine (F.I.R.M.) provides personalized frozen embryo transfer protocols — including the modified natural FET cycle — for patients in Jacksonville, Daytona Beach, Tallahassee, and Valdosta, GA, with care plans tailored to each patient's unique cycle and medical history.
Reviewed by the Physicians of F.I.R.M. — The clinical content on this page reflects the expertise of F.I.R.M.'s board-certified reproductive endocrinologists, including Kevin Winslow, MD, Teresa Erb, MD, Adrienne Gentry, DO, and Viji Sundaram, MD. F.I.R.M. has been recognized by Newsweek as one of America's Best Fertility Clinics and has helped more than 20,000 families grow over 35+ years of practice in North Florida and Southeast Georgia.
A more contemporary way to perform a cryo (frozen) embryo transfer is the modified natural embryo transfer protocol. The concept behind this is to simply perform a frozen embryo transfer at the proper time point during a natural ovulatory menstrual cycle to allow for embryo implantation and development. During such a treatment cycle, the patient’s natural follicle development is followed by ultrasound and blood work. At the time that it is expected that the woman would ovulate, a trigger shot of hCG is typically given to cause ovulation and promote good corpus luteal function, thereby maintaining proper progesterone levels. The day following the follicular trigger shot, a minimal form of Progesterone administration is typically begun.
During the natural cycle no supplemental Estrogen is typically required. The advantage to such a cycle is that there is little need for hormonal support and implantation is ultimately allowed to occur in an environment very closely replicating a natural ovulation. Disadvantages to such a transfer cycle mainly focus on our inability to time the cycle to possibly desired calendar days for transfer, as we are simply following along the natural follicle development. Not all women will be candidates for a modified natural embryo transfer cycle.
Those patients would include women with irregular menstrual cycles, history of recurrent pregnancy loss, gestational carrier cycles, and others. Better suited candidates are women who have had prior spontaneous successful pregnancies and now have infertility issues due to tubal factor or severe male factor. If such a frozen embryo transfer cycle interests you, please consider discussing this with your physician at the F.I.R.M.
In a fully natural FET cycle, the embryo transfer is timed entirely around the patient's natural ovulation with no medications. In a modified natural FET cycle, a small trigger injection — typically hCG or a similar medication — is added to more precisely control the timing of ovulation. This gives the F.I.R.M. team greater flexibility in scheduling the transfer while still allowing the body to prepare the uterine lining naturally.
Modified natural FET cycles are generally suitable for patients who have regular, predictable ovulatory cycles and a good uterine lining response. F.I.R.M.'s board-certified reproductive endocrinologists will evaluate your cycle history, hormone levels, and prior IVF results to determine the most appropriate protocol for your embryo transfer.
The primary medication added in a modified natural FET is a trigger injection to control the exact timing of ovulation. Progesterone support is typically added after ovulation to support implantation. The specific medications and doses are determined by your F.I.R.M. physician based on your individual cycle and response.
A modified natural FET cycle generally follows the patient's natural cycle length — typically around 4 to 5 weeks from the start of monitoring to the embryo transfer. Your F.I.R.M. care team will guide you through each monitoring appointment and provide a personalized timeline.
Yes. F.I.R.M. offers frozen embryo transfer protocols, including the modified natural FET, at its Jacksonville and Daytona Beach locations. Monitoring appointments can be coordinated across F.I.R.M.'s North Florida and Southeast Georgia clinic network. Call (904) 399-5620 or request an appointment online to get started.